Significant progress is being made in delineating the cell origin of acute leukemia. One group of patients has a disease of "null" lymphocyte origin and the other of T lymphocyte origin. These two types of disease have a different prognosis. Therapeutic implications of this discovery are being examined. Broad studies of the immune response combined with special studies of antigens in leukemia are being applied to the problem of the antitumor immune response in man. Treatment to be effective must provide life which is of good quality as well as increased quantity. Ancillary studies on problems such as growth and development are underway. Methods are being developed for maximal use of nonphysician professionals in these areas.